1. Field of the Invention
The present invention relates in general to mufflers for use in an exhaust system of an internal combustion engine of a motor vehicle, and more particularly to the exhaust mufflers of a type which can control the performance thereof in accordance with an operation condition of the engine. More specifically, the present invention is concerned with a pressure sensible valve for use in such controllable exhaust muffler.
2. Description of the Related Art
In order to clarify the task of the present invention, one known pressure sensible valve will be briefly described with reference to FIG. 13 of the accompanying drawings, which is shown in laid-open Japanese Patent Application (Tokkai-Hei) 10-131738.
In FIG. 13, there is shown a controllable exhaust muffler 100 which has the known pressure sensible valve mounted therein. The muffler 100 comprises a casing 101 and two partition walls 101A and 101B which are arranged in the casing 101 to partition the interior of the casing 101 into three chambers A, B and C, as shown. The partition walls 101A and 101B are respectively formed with openings for mounting a passing pipe 102 which extends across the chamber B to connect the chambers A and C. The passing pipe 102 is welded to the partition walls 101A and 100B at the openings. The partition wall 101A is formed around the opening thereof with a tapered depression 104 which is depressed toward the other partition wall 101B. The depression 104 can be closed by a valve plate 107 which is pivotally held by stands 105 mounted on the partition wall 101A. Thus, the tapered depression 104 can serve as a valve seat 103. The valve plate 107 has a tapered periphery 108 that is shaped to mate with the tapered side surface of the depression 104. A pivot shaft 106 extends between the stands 105 to allow the pivoting movement of the valve plate 107 relative to the stands 105. A coil spring 109 is disposed around the pivot shaft 106 to bias the valve plate 107 in a direction to close the depression 104, that is, in a direction to close an outlet opening of the passing pipe 102 which is exposed to the chamber A. The depression 104 has a sealing member 110 disposed on the tapered surface thereof, The sealing member 110 is made of a heat resistant material, such as wire mesh or the like. Usually, due to the biasing force of the coil spring 109, the valve plate 107 is seated in the depression 104 closing the outlet opening of the passing pipe 102, as shown in the drawing. While, when the exhaust pressure in the chamber C exceeds a predetermined value that corresponds to the biasing force of the coil spring 109, the valve plate 107 is lifted from the depression 104 thereby to establish a fluid connection between the chambers A and C. Upon this, the performance of the muffler 100 changes.
However, due to difficulty in assembly, the above-mentioned pressure sensible valve fails to establish an accurate relative positioning between the tapered depression 104 (or valve seat 103) and the valve plate 107. That is, if the relative positioning is not accurately made, exhaust gas leakage tends to occur through the valve, which of course deteriorates the muffling performance of the muffler 100.
It is therefore an object of the present invention to provide a pressure sensible valve for an exhaust muffler, which is free of the above-mentioned drawback.
According to the present invention, there is provided a pressure sensible valve for use in an exhaust muffler, which can be readily assembled while assuring a positioning of a valve plate structure relative to a valve seat structure.
That is, according to the present invention, a sealed condition of the valve is assuredly made in a closed position of the same even when the valve plate structure makes a displacement by some degree relative to the valve seat structure.
According to a first aspect of the present invention, there is provided a valve for use in an exhaust muffler, which comprises a valve seat structure adapted to be secured to an outlet end of a passing pipe installed in the exhaust muffler, the valve seat structure including a flat seat surface portion which extends around the outlet end of the passing pipe; a valve plate structure pivotally connected to the valve seat structure, the valve plate structure including a valve plate portion and a flat sealing portion which forms a peripheral part of the valve plate portion, the valve plate structure having a close position wherein the valve plate portion closes the outlet end of the passing pipe having the flat sealing portion entirely pressed against the flat seat surface of the valve seat structure and an open position wherein the valve plate portion opens the outlet end of the passing pipe having the flat sealing portion separated from the flat seat surface; and a biasing structure which biases the valve plate structure to assume the close position.
According to a second aspect of the present invention, there is provided a valve for use with a passing pipe installed in an exhaust muffler, which comprises a valve seat structure adapted to be secured to an outlet end of a passing pipe installed in the exhaust mufflers the valve seat structure including a collar portion which is adapted to be disposed on an outlet end of the passing pipe and an annular flat seat surface portion which is defined on the collar portion in a manner to extend around the outlet end of the passing pipe; a valve plate structure including a circular valve plate portion and an annular flat sealing portion which forms a peripheral part of the circular valve plate portion, the valve plate structure having a close position wherein the circular valve plate portion closes a circular opening of the collar portion having the annular flat sealing portion entirely pressed against the annular flat seat surface of the valve seat structure and an open position wherein the circular valve plate portion opens the circular opening of the collar portion having the annular flat sealing portion separated from the annular flat seat surface; a pivot structure through which the valve plate structure is pivotally connected to the valve seat structure; an annular seal member which is fixed to one of the annular flat seat surface and the annular flat sealing portion, so that when the valve plate structure takes the close position, the annular seal member is compressed between the annular flat seat surface and the annular flat sealing portion thereby assuring sealing therebetween; and a biasing structure which biases the valve plate structure to assume the close position.
According to a third aspect of the present invention, there is provided a method of assembling a valve, which comprises the steps of (a) preparing a valve seat structure and a valve plate structure, the valve seat structure including a first pair of side wall portions which are formed with first aligned openings which are elliptic in shape, the valve plate structure including a second pair of side wall portions which are formed with second aligned openings which are circular in shape; (b) putting the second side wall portions between the first side wall portions and keeping the second and first side wall portions in such a manner that the first and second aligned openings are all aligned; (c) inserting a pivot shaft into the aligned first and second openings so that the valve plate structure becomes pivotal relative to the valve seat structure about the pivot shaft; (d) positioning the valve plate structure relative to the valve seat structure by moving the pivot shaft in the first aligned openings; and (e) welding the pivot shaft to the first side wall portions while keeping the positioning between the valve plate structure and the valve seat structure.